Metal nano particle and method for surface treating the same

ABSTRACT

Disclosed herein is a method for surface treating metal nano particles, including: surface treating metal nano particles with an alkanol amine containing solution.

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 ofKorean Patent Application Serial No. 10-2012-0120361 entitled “MetalNano Particle and Method for Surface Treating the Same” filed on Oct.29, 2012, which is hereby incorporated by reference in its entirety intothis application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to metal nano particles and a method forsurface treating the same, and more particularly, to a method forsurface treating metal nano particles capable of effectively removingimpurities that remain in metal nano particles having high purity andmetal nano particles synthesized therefor.

2. Description of the Related Art

Generally, a multi-layered chip element such as a multi-layer ceramiccapacitor (MLCC) is manufactured by forming internal electrodes on aplurality of dielectric sheets, laminating the sheets to manufacture alaminate, and forming external electrodes on the laminate. As a materialfor the internal electrode, a metal paste including various types ofmetal nano particles is used. As an example, there is a technology offorming internal electrodes of a multi-layer ceramic capacitor by usinga nickel paste including nickel nano particles.

The metal nano particles are synthesized by methods, such as a liquidphase method, a gas phase method, a plasma and laser using method, andthe like. For example, the nickel nano particles may be synthesized onan organic solvent including a surfactant. The synthesized nickel nanoparticles may be easily dispersed by a nonpolar solvent and are addedwith a polar solvent such as alcohol, acetone, and the like, andrecovered in a power form by a centrifugal separator.

However, the method for synthesizing metal nano particles may relativelyeasily remove the organic solvent and the surfactant among theimpurities remaining on the surfaces of the metal nano particles but mayhardly remove the organic matters among the impurities. In particular,when a metal salt including chloride ion is used as a reactingprecursor, the chloride ion adhered on the surfaces of the synthesizedmetal nano particles may not easily be removed. The impurities such aschloride ion, and the like, degrade the purity of the metal nanoparticles and when intending to form a fine electrode that is a chipcomponent by using the low-purity metal nano particles, the electrodecharacteristics are deteriorated.

RELATED ART DOCUMENT Patent Document

(Patent Document 1) Korean Patent Laid-Open Publication No. 2001-0110693

SUMMARY OF THE INVENTION

An object of the present invention is to provide metal nano particleshaving high purity and a method for surface treating metal nanoparticles.

Another object of the present invention is to provide synthesized metalnano particles having low impurity concentration and a method forsurface treating metal nano particles capable of effectively removingthe impurities remaining on the surfaces of metal nano particles.

Still another object of the present invention is to provide metal nanoparticles having low chloride ion concentration and a method for surfacetreating metal nano particles capable of effectively removing thechloride ions remaining on surfaces of the synthesized metal nanoparticles.

According to an exemplary embodiment of the present invention, there isprovided a method for surface treating metal nano particles, including:surface treating metal nano particles with an alkanol amine containingsolution.

The surface treating of the metal nano particles may include removingchloride ion adhered on the surfaces of the metal nano particles withthe alkanol amine.

The surface treating of the metal nano particles may further includesubstituting chloride ion adhered on the surfaces of the metal nanoparticles into the alkanol amine.

The surface treating of the metal nano particles may further include:preparing a clean solution containing at least one of ethanolamine,diethanaolamine, and triethanolamine; and preparing a mixing solution bymixing the metal nano particles with the cleaning solution.

A concentration of the alkanol amine of the solution may be 10 wt % ormore.

The method for surface treating metal nano particles may furtherinclude: cleaning the metal nano particles with alcohol or toluene toremove a surfactant on the surfaces of the metal nano particles.

The method for surface treating metal nano particles may furtherinclude: drying the metal nano particles.

After the drying of the metal nano particles, the concentration of thechloride ion on the surfaces of the metal nano particles measured byusing ion chromatography may be less than 100 ppm.

After the drying of the metal nano particles, the concentration of thechloride ion on the surfaces of the metal nano particles measured byusing ion chromatography may be less than 10 ppm.

The metal nano particles may be surface-treated with an alkanol aminecontaining solution and after the metal nano particles are dried, theconcentration of the chloride ion on the surfaces of the metal nanoparticles measured by using ion chromatography may be less than 100 ppm.

The concentration of the chloride ion may be less than 10 ppm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating a method for surface treating metalnano particles according to an exemplary embodiment of the presentinvention.

FIG. 2 is a diagram for describing a process of surface treating metalnano particles according to the exemplary embodiment of the presentinvention.

FIG. 3 is a diagram illustrating a multi-layer ceramic capacitormanufactured by using nickel nano particles to which the method forsurface treating metal nano particles according to the exemplaryembodiment of the present invention is applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various advantages and features of the present invention and methodsaccomplishing thereof will become apparent from the followingdescription of embodiments with reference to the accompanying drawings.However, the present invention may be modified in many different formsand it should not be limited to the embodiments set forth herein. Theseembodiments may be provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. Like reference numerals throughout the descriptiondenote like elements.

Terms used in the present specification are for explaining theembodiments rather than limiting the present invention. Unlessexplicitly described to the contrary, a singular form includes a pluralform in the present specification. The word “comprise” and variationssuch as “comprises” or “comprising,” will be understood to imply theinclusion of stated constituents, steps, operations and/or elements butnot the exclusion of any other constituents, steps, operations and/orelements.

Hereinafter, metal nano particles and a method for surface treatingmetal nano particles according to an exemplary embodiment of the presentinvention will be described in detail with reference to the accompanyingdrawings.

FIG. 1 is a flow chart illustrating a method for surface treating metalnano particles according to an exemplary embodiment of the presentinvention and FIG. 2 is a diagram for describing a principle of surfacetreating metal nano particles according to the exemplary embodiment ofthe present invention.

Referring to FIGS. 1 and 2, the method for surface treating metal nanoparticles according to the exemplary embodiment of the present inventionmay include removing impurities 120 remaining on surfaces of synthesizedmetal nano particles 110 (S110), treating the metal nano particles 110with an alkanol amine 130 containing solution (S120), and drying themetal nano particles 110 (S130).

The metal nano particles 110 may be prepared by using various methods ofsynthesizing nano particle. For example, various kinds of the metal nanoparticles 110 may be prepared by using any one of a gas phase method, aliquid phase method, and a plasma and laser using method. As an example,the synthesizing of the metal nano particles 110 may include preparingnickel nano particles using a metal salt including chloride ion as areacting precursor. Various kinds of impurities 120 may remain in thesynthesized metal nano particles 110 in a form in which the impurities120 are adhered on the surfaces of the metal nano particles 110. Theimpurities 120 may include an organic solvent, a surfactant, organicmatters, and the like. The organic matters may include chloride ion.

The impurities 120 remaining on the surfaces of the metal nano particles110 may be removed (S110). The removing of the impurities 120 may beperformed by treating the metal nano particles 110 with alcohol ortoluene. The organic solvent or the surfactant among the impurities 120may be removed regardless of polarity or non-polarity during the processof treating the metal nano particles 110 with alcohol or toluene.However, it may be difficult to remove the organic matters among theimpurities only by the treatment using the alcohol or the toluene. Theorganic matters adhered on the surfaces of the metal nano particles 110may degrade the purity of the metal nano particles 110.

Therefore, the metal nano particles 110 may be surface-treated by usingthe alkanol amine 130 (S120). The surface treating of the metal nanoparticles 110 may be provided to remove the organic matters among theimpurities 120 adhered on the surfaces of the metal nano particles 110.In more detail, in the surface treating of the metal nano particles 110using the alkanol amine 130, the metal nano particles 110 may be mixedwith a cleaning solution. Therefore, the chloride ion that is theorganic matters adhered on the surface of the metal nano particles 110is substituted into the alkanol amine 130, such that the chloride ionmay be removed from the metal nano particles.

Here, as the cleaning solution, a solution including at least one ofethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA) may beused. Further, the cleaning solution may further be added with alcoholsuch as ethanol. In this case, the cleaning solution may be controlledso that the concentration of the alkanol amine becomes at least 10 wt %or more. When the concentration of the alkanol amine is less than 10 wt%, the removal efficiency of the chloride ion is low, such that it maybe difficult to expect the high removal efficiency of impurities.

Meanwhile, the surface treating of the metal nano particles 110 (S120)may further include heating a mixing solution prepared by adding thecleaning solution to the metal nano particles 110 at a predeterminedtemperature. The heating temperature of the mixing solution may beapproximately 60° C. to 100° C. In particular, when the alcohol is addedto the mixing solution, the heating temperature of the mixing solutionmay be higher than 78° C. that is a boiling point of the alcohol.However, a substitution reaction between the alkanol amine 130 and thechloride ion may be performed without heating the mixing solution, suchthat the heating of the mixing solution may be optionally performed.

Further, the metal nano particles 110 may be dried (S130). The drying ofthe metal nano particles 110 may be for removing the alkanol amine 130adhered on the surfaces of the metal nano particles 110. The drying ofthe metal nano particles 110 may include the heat treating of the metalnano particles 110 at a temperature of at least 50° C. or more.Therefore, the alkanol amine 130 adhered to the metal nano particles 110is dried and removed, such that the metal nano particles 110 havingchloride ion concentration less than approximately 100 ppm can beobtained. In particular, the method for surface treating metal nanoparticles according to the exemplary embodiment of the present inventioncan obtain the high-purity metal nano particles 110 having the chlorideion concentration of approximately 10 ppm or less, more preferably, lessthan 5 ppm.

EXAMPLE 1

After the metal nano particles were synthesized, the synthesized metalnano particles were each cleaned with ethanol twice and toluene twice,respectively and were added to a cleaning solution formed of triethanolamine and ethanol to prepare the mixing solution. The mixing solutionwas heated at a temperature of 80° C. Further, after the metal nanoparticles were dried, the amount of chloride ion remaining on thesurfaces of the nano particles was analyzed using ion chromatography.The following Table 1 shows the removal effect of chloride ion over thesurface treating time of a triethanol amine containing solution asdescribed above.

TABLE 1 Chloride Ion Division Concentration (ppm) Prior to surfacetreating 1780 with alkanol amine After 30 minutes of surface 5.6treating with alkanol amine After 10 hours of surface 2.3 treating withalkanol amine

As described above, the final chloride ion concentration of the metalnano particles which are surface treated with the alkanol aminecontaining cleaning solution shown the removal ratio of 99% or more thanthat of the first metal nano particles. That is, the alkanol aminecontaining cleaning solution may show the removal ration of the highchloride ion of the metal nano particles only by the surface treatmentfor a short time of about 30 minutes, such that it was shown that themanufacturing process yield of the nano particles having high purity maybe significantly improved. In particular, the chloride ion concentrationof the metal nano particles may be reduced less than 10 ppm only withthe surface treating of 30 minutes and the chloride ion concentrationmay be reduced less than 5 ppm.

As described above, the method for surface treating metal nano particlesaccording to the exemplary embodiment of the present invention caneffectively remove the chloride ion that is difficult to be relativelyremoved among the impurities 120 adhered on the surface of thesynthesized metal nano particles 110 with the alkanol amine solution. Inparticular, the exemplary embodiment of the present invention may removethe chloride ion of 99% or more within the relatively short processtime, thereby significantly improving the surface treating processingefficiency. Therefore, the method for surface treating metal nanoparticles to the exemplary embodiment of the present inventionsurface-treats the synthesized metal nano particles by using the alkanolamine solution to effectively remove the chloride ion that is difficultto be relatively removed among the impurities remaining on the surfacesof the synthesized metal nano particles, thereby obtaining thehigh-purity metal nano particles having the chloride ion concentrationof approximately 100 ppm, preferably, less than 5 ppm.

To be continued, as described above, various applications of the metalnano particles 110 from which the impurities are removed by the surfacetreating method according to the exemplary embodiment of the presentinvention will be described in detail.

The surface-treated metal nano particles according to the exemplaryembodiment of the present invention may be used as a material forforming internal wirings of the electronic circuit. In particular, inthe case in which the metal nano particles are nickel nano particles,the nickel nano particles have the relatively higher purity and tapdensity and thus, may be suitably used as a material for forming theelectrode of the multi-layer ceramic capacitor (MLCC) that is graduallysmall and thin in recent.

FIG. 3 is a diagram illustrating a multi-layer ceramic capacitormanufactured by using nickel nano particles to which the method forsurface treating metal nano particles according to the exemplaryembodiment of the present invention is applied. Referring to FIG. 3, anickel paste may be prepared by adding an organic binder and an organicsolvent to the nickel nano particles obtained by synthesizing the nickelnano particles and performing the surface treating described withreference to FIGS. 1 and 2 on the synthesized nickel nano particles. Anexample of the organic binder may include ethyl cellulose, and the like,and an example of the organic solvent may include terpineol, dihydroxyterpineol, 1-octanol kerosene, and the like. In this case, the contentsof the nickel paste may be controlled to have 40 wt % to 60 wt % ofnickel nano particles, 0.8 wt % to 4 wt % of organic binder, and 40 wt %to 60 wt % of organic solvent. Here, the conductive paste according tothe exemplary embodiment of the present invention may further includeany one additives among a plasticizer, an anti-viscosity agent, and adispersant.

Further, after the plurality of dielectric sheets 20 are prepared,predetermined internal electrodes 30 of the metal paste may be formed oneach dielectric sheets 20 by a screen printing method. The dielectricsheets 20 are laminated and burned, thereby manufacturing the laminate40. External electrodes 50 electrically connected with the internalelectrodes 30 may be formed at both ends of the laminate 40. In thiscase, the external electrode 50 may be formed using the nickel paste.When the external electrode 50 is formed of the nickel paste, a separateplating process for forming the external electrode 50 may not beperformed. The multi-layer ceramic capacitor 10 having the highelectrode characteristics may be manufactured by the foregoing process.

The foregoing exemplary embodiment of the present invention describe, byway of example, the case in which the metal nano particles according tothe present invention are applied to the chip component elements such asthe multi-layer ceramic capacitor, but the metal nano particlesaccording to the present invention can be applied to various fields. Asanother example, the metal nano particles may be used as a catalyst. Inmore detail, the metal nano particles may be used as a catalyst for afuel cell, a hydrogenation catalyst, a substitute catalyst of Pt invarious chemical reactions, and the like.

According to the exemplary embodiments of the present invention, thechloride ion impurities that are difficult to be relatively removed aretreated with the alkanol amine solution so as to effectively remove thechloride ion impurities, thereby obtaining the metal nano particleshaving the high purity.

According to the exemplary embodiments of the present invention, themethod for surface treating metal nano particles surface-treats thesynthesized metal nano particles by using the alkanol amine solution toeffectively remove the chloride ion that is difficult to be relativelyremoved among the impurities remaining on the surfaces of thesynthesized metal nano particles, thereby obtaining the metal nanoparticles having high purity.

The above detailed description exemplifies the present invention.Further, the above contents just illustrate and describe preferredembodiments of the present invention and the present invention can beused under various combinations, changes, and environments. That is, itwill be appreciated by those skilled in the art that substitutions,modifications and changes may be made in these embodiments withoutdeparting from the principles and spirit of the general inventiveconcept, the scope of which is defined in the appended claims and theirequivalents. Although the exemplary embodiments of the present inventionhave been disclosed for illustrative purposes, those skilled in the artwill appreciate that various modifications, additions and substitutionsare possible, without departing from the scope and spirit of theinvention as disclosed in the accompanying claims. Therefore, thedetailed description of the present invention does not intend to limitthe present invention to the disclosed embodiments. Further, it shouldbe appreciated that the appended claims include even another embodiment.

What is claimed is:
 1. A method for surface treating metal nanoparticles, comprising: surface treating metal nano particles with analkanol amine containing solution.
 2. The method according to claim 1,wherein the surface treating of the metal nano particles includesremoving chloride ion adhered on the surfaces of the metal nanoparticles with the alkanol amine.
 3. The method according to claim 1,wherein the surface treating of the metal nano particles furtherincludes substituting chloride ion adhered on the surfaces of the metalnano particles into the alkanol amine.
 4. The method according to claim1, wherein the surface treating of the metal nano particles furtherincludes: preparing a clean solution containing at least one ofethanolamine, diethanaolamine, and triethanolamine; and preparing amixing solution by mixing the metal nano particles with the cleaningsolution.
 5. The method according to claim 1, wherein a concentration ofthe alkanol amine of the solution is 10 wt % or more.
 6. The methodaccording to claim 1, further comprising cleaning the metal nanoparticles with alcohol or toluene to remove a surfactant on the surfacesof the metal nano particles.
 7. The method according to claim 1, furthercomprising: drying the metal nano particles.
 8. The method according toclaim 7, wherein after the drying of the metal nano particles, theconcentration of the chloride ion on the surfaces of the metal nanoparticles measured by using ion chromatography is less than 100 ppm. 9.The method according to claim 8, wherein after the drying of the metalnano particles, the concentration of the chloride ion on the surfaces ofthe metal nano particles measured by using ion chromatography is lessthan 10 ppm.
 10. Metal nano particles, wherein the metal nano particlesare surface-treated with an alkanol amine containing solution and afterthe metal nano particles are dried, the concentration of the chlorideion on the surfaces of the metal nano particles measured by using ionchromatography is less than 100 ppm.
 11. The Metal nano particlesaccording to claim 10, wherein the concentration of the chloride ion isless than 10 ppm.